1. Field of the Invention
The present invention relates to an oil supply structure of a scroll compressor, and more particularly, to an oil supply structure of a scroll compressor for preventing a slender hole of an oil supply screw from being clogged with sludge, the oil supply screw being provided between a backpressure space, which is defined between an orbiting scroll and a main frame, and a space which is defined between a fixed scroll and the main frame, and adapted to supply oil from the backpressure space into the space.
2. Description of the Related Art
A general scroll compressor, as shown in FIG. 1, includes a main frame 2 and sub frame 3 mounted in a shell 1 at upper and lower locations of the shell 1, a stator 4 press-fitted in the shell 1 between the main frame 2 and the sub frame 3, and a rotor 5 disposed in the stator 4 and adapted to rotate by power applied thereto.
A vertical crank shaft 6 is fixedly inserted into the center of the rotor 5 such that opposite ends thereof are rotatably supported by the main frame 2 and sub frame 3, respectively. Then, the vertical crank shaft 6 is rotated along with the rotor 5.
The scroll compressor further includes a compression unit including an orbiting scroll 7 disposed on an upper end surface of the main frame 2, and a fixed scroll 8 located over the orbiting scroll 7 to be secured to an inner periphery of the shell 1. The orbiting scroll 7 has a lower portion coupled to the crank shaft 6 and an upper portion forming an involute orbiting wrap 7a. The fixed scroll 8 has a fixed wrap 8a configured to be engaged with the orbiting wrap 7a in such a manner that a compression chamber 21 is defined between the fixed wrap 8a and the orbiting wrap 7a. With this configuration, while the orbiting scroll 7 performs an orbiting rotation by rotation of the crank shaft 6, refrigerant gas introduced into the compression chamber 21 can be compressed.
A structure for coupling the crank shaft 6 with the orbiting scroll 7 includes a hollow boss 7b, which protrudes downward from the center of a lower portion of the orbiting scroll 7, and a crank pin 10 which protrudes upward from the center of an upper end surface of the crank shaft 6 by a predetermined distance to be inserted into the hollow boss 7b. A bearing 11 is forcibly press-fitted in the boss 7b, and an eccentric bush 12 is rotatably coupled around the crank pin 10.
In addition, an Oldham's ring 9 serving as anti-rotation device is interposed between the main frame 2 and the orbiting scroll 7. An oil supply path 6a is vertically defined in the crank shaft 6 throughout the overall length of the crank shaft 6. A pair of upper and lower balancing weights 13 and 14 are arranged above and below the rotor 5, respectively, to prevent unbalanced rotation of the crank shaft 6 that may be caused by the crank pin 10.
If high-pressure refrigerant gas compressed in the above described compression unit is discharged through an outlet 17 of the fixed scroll 8, the high-pressure refrigerant gas imparts a direct shock to a top cap 1a constituting an upper end of the shell 1, thus causing generation of noise. Accordingly, to reduce the noise, a muffler 22 is mounted above the fixed scroll 8. The muffler 22, as shown in FIG. 2, takes the form of a cover.
In addition to this noise reduction function, the muffler 22 has a function of isolating a suction pressure from a discharge pressure, namely, a low-pressure portion from a high pressure portion when the scroll compressor has a high-pressure structure wherein a lower region of the compressor is filled with the high-pressure refrigerant gas discharged from the compression unit. The fixed scroll 8 has guidance paths 23 to guide the compressed refrigerant gas in the muffler 22 into the lower region of the compressor.
In FIG. 1, reference numerals 15 and 16 designate a suction pipe and discharge pipe, respectively, and reference numeral 18 designates a discharge chamber. Also, reference numerals 19 and 20 designate oil and an oil propeller, respectively.
In the scroll compressor having the above described configuration, if the rotor 5 rotates in the stator 4 upon receiving power, the crank shaft 6 is rotated by the rotor 5, thus causing the orbiting scroll 7, which is coupled to the crank shaft 6 by use of the crank pin 10, to perform an orbiting movement along an orbiting radius between the center of the crank shaft 6 and the center of the orbiting scroll 7.
Accordingly, the compression chamber 21, which is defined between the orbiting wrap 7a and the fixed wrap 8a, has a volume reduction by continuous orbiting movement of the orbiting scroll 7, resulting in compression of refrigerant gas suctioned thereinto. The compressed high-pressure refrigerant gas is discharged into the discharge chamber 18 through the outlet 17 of the fixed scroll 8. In turn, the refrigerant gas in the discharge chamber 18 is guided into the lower region of the compressor through the guidance paths 23 of the fixed scroll 8, and thereafter, is discharged to the outside through the discharge pipe 16.
FIG. 2 is a partially enlarged sectional view of FIG. 1.
As shown in FIG. 2, the main frame 2 has an oil supply screw 24. During operation of the compressor, the oil supply screw 24 allows oil, which is supplied through the crank shaft 6 into a backpressure space C1, which is defined between the orbiting scroll 7 and the main frame 2 and maintains a high pressure, into a space C2 which is defined between the fixed scroll 8 and the main frame 2 and maintains a low pressure.
The oil supply screw 24, as shown in FIG. 3, has a stepped screw body 25 having upper and lower portions of different diameters, The upper larger diameter portion of the screw body 25 is externally formed with screw threads 26, to allow the oil supply screw 24 to be screwed into a screw bore 2a formed in the main frame 2.
An orifice 27 is perforated through the center of the screw body 25. To allow an appropriate amount of oil to be supplied therethrough without interference of a discharge pressure of the oil, the orifice 27 includes a center hole 28 perforated in the upper portion of the screw body 25 and a slender hole 29 perforated in the lower portion of the screw body 25 to communicate with the center hole 28. The slender hole 29 has a smaller diameter than that of the center hole 28 and is drilled to be positioned at the center of the center hole 28.
However, in the oil supply screw of the conventional scroll compressor, since the slender hole constituting the orifice has an extremely small diameter and an entrance end thereof has a flat plane configuration, various impurities and sludge contained in the oil may accumulate at the entrance end, and be introduced into the slender hole of the oil supply screw.
Accordingly, there is a problem in that the slender hole of the oil supply screw may be clogged with the various impurities and sludge contained in the oil. This hinders an appropriate amount of oil to be supplied into the compression unit, and hence, results in deterioration in the performance and reliability of the compressor.
Another problem of the conventional oil supply structure of the scroll compressor is that the slender hole constituting the orifice of the oil supply screw has an extremely small diameter but also as an excessively long length as stated above, and thus, is difficult to be processed. As a result, the conventional oil supply structure suffers from an increase in processing price and thus, is not economical.
A further problem of the conventional scroll compressor is that oil is continuously supplied from the backpressure space having a high pressure into the space having a low pressure, thus causing an unnecessary increase in the supply amount of oil. Moreover, the oil is not supplied directly to thrust planes of the orbiting scroll and main frame, but supplied into the space between the fixed scroll and the main frame, resulting in inefficient oil supply.
Yet another problem is that the slender hole of the oil supply screw must have a very high slenderness ratio to satisfy a requirement for supplying an appropriate amount of oil into the scroll compressor. This disadvantages causes difficulty in hole processing as well as very poor yield (i.e. a low rate of the percentage of a theoretically expected supply amount of oil compared to the actually supplied amount of oil). The difficulty in hole processing becomes a factor of increasing high processing costs and the manufacturing costs of the compressor, and thus, results in degradation of economical efficiency.